I have a cheap plastic mount 14-42mm
and IMVHO it's a perfectly adequate kit lens, in fact I'd say that on a Panasonic body it gives better results than many an entry level APS-C DSLR + 17-50mm lit lens combo
The Panasonic combo may "cheat" to a degree to get that performance but they're all doing in body corrections these days so maybe it's only cheating when Panasonic do it but becomes perfectly acceptable when Canon do it
Regarding the cheap build... Mine still hasn't fallen apart and for the price (next to nothing) it's (IMVHO) a perfectly good kit lens for occasional or even regular use.
I use primes 99.9% of the time but if I want a kit zoom my humble 14-42mm is there and has never let me down and I'd bet a pretty penny that picking 14-42mm images from 14-45mm images would be a very hard task